2) What is an Entity?

Ans: It is a 'thing' in the real world with an independent existence.

3) What is an attribute?

Ans: It is a particular property, which describes the entity.

4) What is E-R model?

Ans: This data model is based on real world that consists of basic objects called entities and of relationship among these objects. Entities are described in a database by a set of attributes.

5) What is database integrity?

Ans: Database integrity imposed to a column to follow certain rules.

There are two-database integrity one is entity integrity and another one is referential integrity.

6) What is data Redundancy?

Ans: If there are repeated values in a table .Its called redundancy.

7) What is entity integrity?

Ans: Entity Integrity states that Primary key cannot have NULL value.

8) What is referential integrity?

Ans: Referential Integrity: States that Foreign Key can be either a NULL.

Value or should be Primary Key value of other relation.

9) Write a query for selecting data from multiple tables?

Ans: SELECT employee.name, employee.addr, department.dept_name form employee, department

Where employee.emp_id = department.emp_id;

(EQUI-JOIN)

10) Write a query for selecting data using order by clause?

Ans: select * from EMP order by emp_id ASC/DESC;

11) When do we use GROUP by Clause?

Ans: We use GROUP by clause to divide the data in multiple groups. Suppose I have 100 employees in employee table and each and every employee is allocated to a branch. If there are 4 branches then multiple employee will be allocated to a specific branch. In this scenario I can use GROUP by branch to select employee group by branch.

12) Write a query for selecting data using group by/where/between/in clause?

Ans: select * from EMP group by branch_no;

Select name, addr from emp where emp_id=2;

Select * from emp where salary between 5000 and 10000;

Select * from emp where addr in(‘kolkata','delhi');

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